MySQL join on three tables EAV model - mysql

Question

Kindly consider the following tables:
invoices
+-----------+----+------------+--------+---------+
| accountid | id | customerid | total | balance |
+-----------+----+------------+--------+---------+
| 1 | 2 | 167909 | 120060 | 120060 |
+-----------+----+------------+--------+---------+
invoices_attributes
+-----------+----+--------------+
| accountid | id | name |
+-----------+----+--------------+
| 1 | 1 | registration |
+-----------+----+--------------+
| 1 | 2 | claimnumber |
+-----------+----+--------------+
| 1 | 3 | jobid |
+-----------+----+--------------+
invoices_attributes_values
+------------------+-------------+-----------+---------------+
| attributevalueid | attributeid | invoiceid | value |
+------------------+-------------+-----------+---------------+
| 1 | 1 | 2 | ABC 126L |
+------------------+-------------+-----------+---------------+
| 2 | 2 | 2 | ABZ123 |
+------------------+-------------+-----------+---------------+
| 3 | 3 | 2 | MARY DOE |
+------------------+-------------+-----------+---------------+
Through the help of Eugen Rieck's original answer I was able to make the following query
SELECT
invoices.accountid,
invoices.id AS invoiceid,
invoices.customerid,
invoices.total,
registration.value AS registration,
claimnumber.value AS claimnumber,
jobid.value as jobid
FROM
invoices
LEFT JOIN invoice_attributes ON invoices.accountid=invoice_attributes.accountid
LEFT JOIN invoice_attribute_values AS registration ON registration.attributeid = invoice_attributes.id AND invoices.id = registration.invoiceid AND invoice_attributes.name = 'registration'
LEFT JOIN invoice_attribute_values AS claimnumber ON claimnumber.attributeid = invoice_attributes.id AND invoices.id = claimnumber.invoiceid AND invoice_attributes.name = 'claimnumber'
LEFT JOIN invoice_attribute_values AS jobid ON jobid.attributeid = invoice_attributes.id AND invoices.id = jobid.invoiceid AND invoice_attributes.name = 'jobid'
Which gave the following result
+-----------+-----------+------------+--------+--------------+-------------+----------+
| accountid | invoiceid | customerid | total | registration | claimnumber | jobid |
+-----------+-----------+------------+--------+--------------+-------------+----------+
| 1 | 2 | 167909 | 120060 | NULL | NULL | MARY DOE |
+-----------+-----------+------------+--------+--------------+-------------+----------+
| 1 | 2 | 167909 | 120060 | NULL | ABZ123 | NULL |
+-----------+-----------+------------+--------+--------------+-------------+----------+
| 1 | 2 | 167909 | 120060 | ABC 126L | NULL | NULL |
+-----------+-----------+------------+--------+--------------+-------------+----------+
When I GROUP BY invoices.id some of the columns (registration, claimnumner or job) will become NULL. I desire the result to be as:
+-----------+-----------+------------+--------+--------------+-------------+----------+
| accountid | invoiceid | customerid | total | registration | claimnumber | jobid |
+-----------+-----------+------------+--------+--------------+-------------+----------+
| 1 | 2 | 167909 | 120060 | ABC 126L | ABZ123 | MARY DOE |
+-----------+-----------+------------+--------+--------------+-------------+----------+
How can the query be modified to get the result above?

Answer 1

SQL has no provision to make the columns dependant on the data. You could however create a query with ALL possible attributes along the lines of
Basically you want to renormalize an EVA structure - this is of course possible:
SELECT
invoices.accountid,
invoices.id AS invoiceid
invoices.customerid,
invoices.total,
jobids.value AS jobid -- one of these lines per attriubute
FROM
invoices
LEFT JOIN invoices_attributes ON invoices.accountid=invoices_attributes.accountid
-- One of the following joins per attribute
LEFT JOIN invoices_attributes_values AS jobids
ON jobids.attr_id=invoices_attributes.attr_id
AND jobids.accountid=invoices.accountid
AND jobids.invoiceid=invoices.id
AND invoices_attributes.attr_name='jobid'